Technical Field
The present disclosure relates generally to fluid dynamics and mechanical engineering for rotating machines like subsea pumps and subsea compressors. More particularly, the present disclosure relates to dynamic seal equipped subsea fluid processing systems configured to process high-temperature process fluids.
Background
Within subsea machines having rotating elements, such as pumps and compressors, dynamic seals play an important role. The dynamic seals are used to seal-off the lubrication fluid from the fluid being processed (e.g. the fluid being pumped or compressed). The lubrication system (also known as the barrier fluid system) is typically designed to be maintained at a higher pressure than the fluid being processed. A primary reason for this is that the barrier fluid is maintained as a clean fluid provide machine lubrication and cooling. Further, the barrier fluid will act as a barrier to materials, which may be present in the processed fluid. In the case of oil and gas produced from subterranean reservoirs, material in the processed fluid can include sand, H2S and scale, all of which is desirable to be kept away from the dynamic seals.
A dynamic seal is typically made from materials such as high alloy steel, titanium and/or silicon carbide. The silicon carbide is a material very resistant to wear due to high tensile strength and smooth surface resulting in low friction properties. The seal includes components made of different material that may be affected by pressure and temperature in different ways.
Within subsea technology, there are particular locations, such as the Gulf of Mexico, where fields exhibit relatively high pressures and/or high temperatures. In order to maintain the performance of the seals, there is a need to address consequences of exposure to such high temperatures and/or high pressures. For high process pressure fields, a known technique is to compensate with a higher barrier fluid pressure in order for the seal to experience the same pressure differential.
As for high process fluid temperatures, some limitations relate to material used to manufacture the seal. For example, the relationship between temperature and component shrinkage is an important parameter for engineering packing/containment designs. In designing high temperature seals, an important consideration is the residual strain that might occur within the component material (like silicon carbide) when at low temperature conditions. On the other hand, at high temperatures there is a tendency to have less component shrinkage due to thermal expansion in packing/containment material.